1. Technical Field
The present invention relates to a display controller, an electronic instrument, and a method of supplying image data.
2. Related Art
In recent years, display panels represented by liquid crystal display (LCD) panels are often implemented to portable devices (electronic instruments, in a broad sense) such as mobile phones. The display panels are driven by display drivers in accordance with image data. The image data can be taken by, for example, camera modules, or generated and/or processed by host systems. The display drivers perform drive control of the display panels in accordance with the image data and sync signals for display.
The display controllers supply the image data and the sync signals for display as a substitute for the hosts to reduce processing loads of the hosts. Some display controllers are equipped with memory devices that function as video memories for the sake of low power consumption.
Incidentally, the portable device to be provided with the display panel houses a camera module, and is arranged to display the image taken by the camera module on the display panel. In this case, the image taken by the camera module is once stored in the memory of the display controller, and then supplied to the display driver.
However, the period of writing the image data from the camera module (writing rate) is not necessary match the period of reading the image data for supplying to the display driver (reading rate). Therefore, if the capacity of the memory in the display controller is no more than just for storing one frame of image data, the image data cannot be supplied to the display driver without lacking of the image data.
Further, the orientation of the image corresponding to the image data taken by the camera module is generally fixed. Therefore, the image data from the camera module is supplied to the display driver with the orientation of the image rotated in the display controller. However, if the orientation of the image is rotated for displaying the image in the display panel, the capacity of the memory in the display controller prepared as much as the amount corresponding to two frames is not sufficient. In this case, the area of the image data for one frame in the reading process is overwritten with the image data for the succeeding frame, thus degrading the quality of the image displayed on the display panel. Therefore, the memory of the display controller is required to have the capacity of at least three frames.
The present invention addresses the above technical requirement and has an advantage of providing a display controller, an electronic instrument, and a method of supplying image data each capable of supplying image data with no missing part thus preventing image degradation.